EPOS4 / IDX: Calcul de la puissance du moteur électrique

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Topic:

• How can the electrical power of a motor driven by an EPOS4 be measured or calculated?

Solution:

Important:
The following information is just valid for an EPOS4 or IDX with firmware version 0x170 (or higher) and EPOS Studio V3.7 (or higher). These updates will be released in May 2021 and ready for download by each maxon EPOS4 product website (e.g. http://epos.maxongroup.com) as part of the "EPOS Setup" installation package. Please always install the complete package. This ensures that you have the latest software, firmware, library and documents. Update the firmware of your EPOS4 (or IDX) then.

If there is an EPOS4 (or IDX) based on the firmware version 0x170 (or higher) in use, it is possible to measure and record all relevant data which is required to calculate the electrical power (PEl.Motor) going into the motor. 

Relevant EPOS4 objects:

• Power supply voltage
  EPOS4: Object 0x2200/01 [0.1V]
  
  This object holds the power supply voltage. Typically the power supply voltage will have an almost fixed level.  Only during deceleration of the drive there is some energy recovery present which can result in an increase of the supply voltage level..
  Although the EPOS4 object "Power supply voltage" (0x2200/01) is not PDO mappable, it can be recorded by EPOS Studio's "Data Recorder" or polled by any master device. 
  
  
• Current actual value averaged
  EPOS4: Object 0x30D1/01 [mA]
  
  It is recommended to read the "Current actual value averaged" because this is a filtered more stable motor current value which has less impact due to current measurement noise. 
  The EPOS4 object "Current actual value averaged" (0x30D1/01) is PDO mappable and thus allows (in case of a real-time CANopen or EtherCAT master) a fast cyclic transmission by a SYNC PDO holding the "PWM duty cycle" too. 
  
  
• PWM duty cycle actual value
  EPOS4 (FW>=0x170): 0x3203/01 [1/1000]
  
  The "PWM duty cycle" is required to calculate the motor voltage. Its value cannot be accessed by the ESCON or EPOS4 firmware versions before 0x170. Due to the fact that it is required for motor power calculation the new object "PWM duty cycle actual value" (0x3203/01) had been added to EPOS4 firmware versions 0x170 or higher.
  The EPOS4 object "PWM duty cycle actual value" (0x3203/01) is PDO mappable and thus allows (in case of a real-time CANopen or EtherCAT master) a fast cyclic transmission by a SYNC PDO holding the "Current actual value averaged" too.

All of the mentioned objects can be recorded by EPOS Studio's "Data Recorder" or polled by any master device.

Calculation of motor voltage:

• Motor voltage = "Power supply voltage" x "PWM duty cycle"
• In case of an EPOS4 (FW>=0x170):
  Motor voltage [mV] = (Object 0x2200/01 x Object 0x3203/01) / 10

Calculation of the electrical motor power:

• Power = "Motor voltage" x "Motor current"
• In case of an EPOS4 (FW>=0x170):
  Power [mW] = (Object 0x2200/01 x Object 0x3203/01 x Object 0x30D1/01) / 10000 

Cross Reference:

• Motor controllers: Input current versus Motor current, Power Conversion